Process for forming a coating on a substrate using a silsesquioxane resin

ABSTRACT

The present invention provides a relatively simple synthesis procedure for the formation of silane hydrolyzate compositions of the formula ##STR1## where R is hydrogen or a methyl group, n is an integer greater than about 8, and x is a number between 0 and 2. The hydrolyzate compositions are metastable in solvent solution, but become insoluble after coating on a substrate. The resins are useful as planarizing coatings for substrates such as electronic devices and can be ceramified by subjecting them to an oxidizing atmosphere at a temperature of between about 100° to 1000° C. to form ceramic or ceramic-like coatings on such substrates.

This is a divisional of copending application Ser. No. 07/590,710 filedOct. 1, 1990, now U.S. Pat. No. 5,045,592, which is a divisional of07/386,450 filed 7/28/89, now U.S. Pat. No. 4,999,397.

BACKGROUND OF THE INVENTION

This invention relates to metastable silane hydrolyzate solutions andmethods for their preparation, and more particularly to the use of suchmetastable solutions to coat substrates with protective films ofinsoluble silsesquioxane resins. Such coatings can then be ceramified byheating to form planarizing coatings on substrates.

Condensed hydrogen silsesquioxane resins (HSiO_(3/2))_(n), particularlythose soluble resins having a low molecular weight (i.e., where n>8 buttotal molecular weight is less than 50,000), are known. Hydrogensilsesquioxane resins have found use as protective coatings applied overmetal substrates, as primer coatings to increase adhesion of othersealant coatings to a surface, and as cross-linking agents for siliconeelastomer resins. More recently, condensed hydrogen silsesquioxaneresins have been proposed as ceramic precursors for planarizing layerson electronic devices. See, for example, Haluska et al, U.S. Pat. Nos.4,753,855 and 4,756,977.

Early methods for the preparation of hydrogen silsesquioxane inhydrocarbon solvents resulted in a resin which was not fully condensed,i.e. the resin contained residual end blocking hydroxyl or alkoxy groupsattached to silicon atoms. Such hydrogen silsesquioxane resins weretaught to be susceptible to further condensation to form insoluble gels.See Boldebuck, U.S. Pat. No. 2,901,460, for a discussion of hydrolysisreactions of chlorosilanes.

Collins and Frye, U.S. Pat. No. 3,615,272 and J. Amer. Chem. Soc. 92:19(1970), reported the synthesis of a fully condensed hydrogensilsesquioxane resin, now known to have contained in the range of140-330 ppm silanol content, which was soluble in nonpolar organicsolvents such as benzene and hexane. The Collins and Frye method addedtrichloro-, trimethoxy-, or triacetoxysilanes in a hydrocarbon solventto a two phase reaction medium comprising a concentrated sulfuric acidphase and an aromatic hydrocarbon phase such as benzene, to effectcondensation of the silanes.

The fully condensed hydrogen silsesquioxane is recovered by washing thereaction mixture with water until neutral and then evaporating thehydrocarbon solvent. However, the process requires the use of both acorrosive acid and an aromatic hydrocarbon in the synthesis. Further,the resin remains soluble even after coating on a substrate, making itundesirable for planarization building up thicker coatings throughmultiple applications as each successive coating application willredissolve the previously applied coating unless a catalyst orcrosslinking agent is added prior to deposition.

Japanese Kokai Patent No. 60-86017 also reports a process for thepreparation of a soluble, fully condensed hydrogen silsesquioxane resinby dissolving a trichlorosilane reactant in a water-saturated organicsolvent. The trichlorosilane is hydrolyzed and condensed by bubbling aninert gas and water vapor through the reaction solution. It is taughtthat care must be taken not to form a separate water phase during thereaction as this results in the formation of an insoluble polycondensedgel product. Consensable silanol (Si--OH) groups are end-blocked by theaddition of trimethyl chlorosilane as a silylating agent.

Others have reported the formation of siloxane compositions when achlorosilane starting material is reacted with a metal oxide. Forexample, Hyde, U.S. Pat. Nos. 2,629,725 and 2,580,852, teaches thereaction of chlorosilanes with metal oxides such as copper, zinc,manganese, and magnesium oxides to form organosiloxanes. The formationof certain cyclic trimers, in the form of substituted cyclotrisiloxanes,by the reaction between chlorosilanes and metal oxides has also beenreported. See, Takiguchi et al, J. Org. Chem., 25, 310 (1960) and Wu,U.S. Pat. No. 3,876,677. More recently, Marko et al, U.S. Pat. No.4,578,494 has taught the reaction of halosilanes in the presence ofcertain metal oxides and sulfolane to form polysiloxanes.

However, there still remains a need in the art for a relatively simplesynthesis procedure which results in the formation of curablesilsesquioxane resin solutions and which avoids the use of corrosiveacid and/or aromatic hydrocarbon media. Further, the need still existsin the art for silane-containing hydrolyzate which is metastable insolvent solution. Still further, the need exists for a silane-containinghydrolyzates which form an insoluble silsesquioxane resins after coatingon a substrate, and which can be repeatedly applied to form relativelythick coatings on substrates.

SUMMARY OF THE INVENTION

The present invention meets that need by providing a relatively simplesynthesis procedure for the formation of silane hydrolyzates which forminsoluble hydrogen or hydrogen and methyl copolymer silsesquioxaneresins upon solvent removal. The hydrolyzates compositions aremetastable in solvent solution, but become insoluble after coating on asubstrate. The hydrolyzate compositions are described as metastablebecause relatively small changes in the solvent solution will result ingelling of the hydrolyzate. The resins are useful as planarizingcoatings for substrates such as electronic devices and can be ceramifiedby heating them to form ceramic or ceramic-like coatings on suchsubstrates.

According to one aspect of the present invention, a method for thepreparation of a metastable silane hydrolyzate of the formula ##STR2##where R is hydrogen or a methyl group, n is an integer greater thanabout 8, x is a number between 0 and 2, and the product produced therebyhas a silanol content of about 1-10% by weight is provided. For asubstantial majority of instances, x will be a number which is lessthan 1. For example, where x=0.06, the silane hydrolyzate will have asilanol content of about 2%. Where x=0.26, the silane hydrolyzate willhave a silanol content of about 8%. Preferably, hydrogen makes up atleast 50% of the R groups on the silane hydrolyzate.

The method includes the steps of adding to a water or hydrochloricacid-containing polar organic solvent a chlorosilane of the formulaRSiCl₃, where R is hydrogen or a methyl group, to form a reactionmixture. At least a substantially stoichiometric amount of a metal oxideis also added to the reaction mixture. The metal oxide acts as ascavenger for hydrogen chloride and as a source of continuous waterformation during the reaction.

The reaction is initiated by the addition of an effective amount ofeither water or hydrochloric acid to the reaction mixture. An effectiveamount of water or hydrochloric acid is substantially less than astoichiometric amount (based on moles of chlorosilane reactant), and maybe less than 10% of the stoichiometric amount. Additionally, the amountof water or hydrochloric acid present is insufficient to form a separateaqueous phase in the reaction mixture.

Small amounts of hydrochloric acid have been found to initiate thehydrolysis reaction due to the reaction of the metal oxide with the acidto form water and a metal chloride. Preferably, the metal oxide isselected so that an insoluble metal chloride precipitate forms,resulting in easy removal from the hydrolyzate in solution. Washing thehydrolyzate results in a composition having a very low residual chloridecontent (i.e., less than 500 ppm residual chloride). Once an effectiveamount of water is present, the chlorosilane then reacts in the reactionmixture to effect hydrolysis and condensation thereof to form themetastable silane hydrolyzate.

In a preferred embodiment, the metal oxide is selected from the groupconsisting of CuO, ZnO, MgO, CaO, Cu₂ O, and mixtures thereof. Theorganic polar solvent is selected for its capability to hydrogen bondwith residual silanol groups in the hydrolyzate. The solvent isnon-sulfur containing and is an aprotic oxygenated solvent preferablyselected from the group consisting of ketones, esters, and mixturesthereof. Specific examples of solvents useful in the practice of thepresent invention include ethyl acetate, methyl isobutyl ketone, t-butylacetate, diethyl ether, and mixtures thereof. The concentration of theresulting hydrolyzate in the solvent is preferably maintained at fromabout 1 to about 25% by weight, with lower concentrations, i.e.,concentrations of about 5 weight % or less, having the longest stabilityin solution.

The process of the present invention produces a composition in which thesilanol content of the dissolved hydrolyzate is from about 1-10% byweight, and preferably from about 4-8% by weight. These silanol groupsin the hydrolyzate are believed to hydrogen bond with the solvent,accounting for their stability in solution. Subsequent addition of asolvent which is incapable of hydrogen bonding, and/or evaporation ofthe hydrogen-bonding solvent, causes the hydrolyzate composition tocondense to an insoluble product with only 0.2-0.9% silanol contentremaining.

Another aspect of the present invention is directed to the metastablesilane hydrolyzate solutions in which a non-sulfur containing polarorganic solvent contains therein a composition of the formula ##STR3##where R is hydrogen or a methyl group, n is an integer greater thanabout 8, x is a number between 0 and 2, and where the silanol content ofthe composition is from about 1-10% by weight, and preferably about 4-8%by weight. Preferably, the concentration of the hydrolyzate in solutionis from about 1 to about 25% by weight. Again, the non-sulfur containingorganic polar solvent is selected for its ability to hydrogen bond withthe silanol groups in the hydrolyzate, and is preferably selected fromthe group consisting of ethyl acetate, methyl isobutyl ketone, t-butylacetate, diethyl ether, and mixtures thereof.

The present invention may be used to form a protective coating of asilsesquioxane resin on a substrate. That process includes the steps ofcoating the substrate with a solution comprising a non-sulfur containingpolar organic solvent containing therein a hydrolyzate composition ofthe formula ##STR4## where R is hydrogen or a methyl group, n is aninteger greater than about 8, x, is a number between 0 and 2, and wherethe silanol content of the composition is from about 1-10% by weight,and preferably about 4-8% by weight, and then evaporating the solvent tocondense the silanols and thereby deposit an insoluble silsesquioxaneresin coating on the substrate which contains about 0.2-0.9% residualsilanol groups. The insoluble silsesquioxane resin coating may then beconverted to a ceramic or ceramic-like coating by subjecting the coatingto an oxidizing atmosphere at a temperature of between about 100° toabout 1000° C.

The metastable silane-containing hydrolyzate of the present inventionmay be applied to a substrate by any of a number of known procedures.For example, the solution containing the hydrolyzate may be coated ontothe substrate by spray coating, dip coating, flow coating, or spincoating. Use of the metastable hydrolyzate of the present invention isparticularly advantageous for applying planarizing coatings tosubstrates such as electronic devices as a first layer in a multilayercoating. Because the resin dries to an insoluble coating, a number ofthin coating layers may be readily built up.

Accordingly, it is an object of the present invention to provide arelatively simple synthesis procedure for the formation ofsilane-containing hydrolyzate compositions which are metastable insolvent solution, but become insoluble hydrogen or hydrogen and methylcopolymer silsesquioxane resins after coating on a substrate. This, andother objects and advantages of the present invention, will becomeapparent from the following detailed description and the appendedclaims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a process, and a product resultingtherefrom, which is useful in forming insoluble hydrogen and hydrogenand methyl copolymer silsesquioxane resin coatings on substrates. Theinvention is particularly useful in coating substrates which aresusceptible to the adverse effects of moisture and other environmentalcontaminants such as electronic components and circuitry. The lowresidual chloride content of the resin (i.e., less than 550 ppm residualchloride is also advantageous). The insoluble silsesquioxane resincoatings made by the process of the present invention make excellentprecursors for conversion to silica films as well as provide an adherentbase coating for subsequent applications of additional coatings such aspassivation and barrier layers to provide complete hermeticity forelectronic components and circuitry.

The process of the present invention utilizes as a starting material achlorosilane of the formula RSiCl₃, where R is hydrogen or a methylgroup. The chlorosilane starting material is placed in a water orhydrochloric acid-containing polar organic solvent which also contains asubstantially stoichiometric amount of a metal oxide is added to thereaction mixture where it is believed to react as follows:

    RSiCl.sub.3 +H.sub.2 O→R-Si hydrolyzate+HCl         (Eq. 1)

    2HCl+MO→MCl.sub.2 +H.sub.2 O                        (Eq. 2)

The hydrolyzate which is formed is believed to have the formula ##STR5##where R is hydrogen or a methyl group, n is an integer greater thanabout 8, and x is a number between 0 and 2. Where the chlorosilanestarting material comprises a mixture of hydrogen and methyl moieties,the resulting hydrolyzate is a copolymer. The ratio of hydrogen tomethyl in the copolymer may vary over a broad range. But preferably, themole ratio of hydrogen to methyl in the copolymer is equal to or greaterthan one.

As can be seen from Equation 2 above, the metal oxide is believed toreact with the hydrochloric acid to form the corresponding metalchloride and water. Accordingly, the presence of either small effectiveamounts of water or hydrochloric acid will initiate the reaction. Themetal oxide utilized may be CuO, ZnO, MgO, CaO, Cu₂ O, and mixturesthereof. It is not believed that the process of the present inventioninvolves the reaction of a chlorosilane directly with a metal oxide.Rather, it is believed that the metal oxide acts only in the role of ahydrochloric acid scavenger and a controlled regenerator of water. Thepresence of at least an effective amount of water or hydrochloric acidis believed necessary for the reaction to proceed.

The non-sulfur containing organic polar solvent is selected for itscapability to hydrogen bond with residual silanol groups in thehydrolyzate. The solvent is preferably selected from the groupconsisting of ketones, esters, ethers, and mixtures thereof. Specificexamples of suitable solvents include ethyl acetate, methyl isobutylketone, t-butyl acetate, diethyl ether, and mixtures thereof. Theconcentration of the resulting hydrolyzate in the solvent is preferablymaintained at from about 1 to about 25% by weight, with lowerconcentrations, i.e., concentrations of about 5 weight % or less, havingthe longest stability in solution. Generally, solutions havingconcentrations of 5 weight % or less can maintain stability on the orderof months, while solutions having increasing concentrations of thehydrolyzate may maintain stability on the order of days or hours.

The process of the present invention produces a composition in which thesilanol content of the hydrolyzate is from about 1-10% by weight, andpreferably about 4-8% by weight. This is in sharp contrast to prior artprocedures which produce nearly fully condensed, soluble hydrogensilsesquioxane resins having silanol levels of only about 140-330 partsper million (i.e., from about 0.01 to 0.03% by weight silanol). Thesesilanol groups in the hydrolyzate of the present invention are believedto hydrogen bond with the solvent to give the product its metastabilityin solution. Subsequent addition of a solvent which is incapable ofhydrogen bonding, and/or the evaporation of the hydrogen bondingsolvent, causes the hydrolyzate composition to condense to an insolubleproduct with about a 2000-9000 ppm residual silanol content.

The present invention may be used to form a protective coating of aninsoluble silsesquioxane resin on a substrate such as an electroniccomponent or circuit. That process includes the steps of coating thesubstrate with a solution comprising a non-sulfur containing polarorganic solvent containing therein the metastable hydrolyzatecomposition of the present invention, and then evaporating the solvent,thereby depositing an insoluble silsesquioxane coating on the substrate.The insoluble silsesquioxane coating may then be converted to a ceramicor ceramic-like coating by subjecting the coating to an oxidizingatmosphere at a temperature of between about 100° to about 1000° C.

The metastable silane-containing hydrolyzate of the present inventionmay be applied to a substrate by any of a number of known procedures.For example, the solution containing the hydrolyzate may be coated ontothe substrate by spray coating, dip coating, flow coating, or spincoating. Use of the metastable hydrolyzate of the present invention isparticularly advantageous for applying planarizing coatings tosubstrates such as electronic devices as a first layer in a multilayercoating. Because the resin dries to an insoluble coating, a number ofthin coating layers may be readily built up. Additionally, thesilsesquioxane resin layer provides an adherent base for additionalcoatings such as passivation layers and barrier layers.

In order that the invention may be more readily understood, reference ismade to the following examples, which are intended to illustrate theinvention, but are not to be taken as limiting the scope thereof.

EXAMPLE 1

In order to evaluate the effect of water initially present in thereaction mixture, both the ethyl acetate solvent and the copper (II)oxide were dried prior to use. The ethyl acetate was distilled overphosphorous pentoxide. The copper (II) oxide was placed into a vialunder vacuum and heated for several hours. A total of 2.70 gtrichlorosilane was added over a one minute period to a rapidly stirredmixture of 2.36 g "dry" CuO in 25 ml "dry" ethyl acetate. No exotherm orcolor change was observed prior to the addition of water. Afterapproximately 30 minutes, a small amount of water (approximately 0.15mL) was added to the reaction medium. The reaction proceeded and within30 minutes, a black/brown solution formed. The clear solution wasdecanted away from the black/brown CuO/CuCl₂ mixture and washed withdistilled water. The clear solution was placed into an evaporation dish.A total of 0.54 g (50 percent yield) of insoluble hydrogensilsesquioxane was collected after solvent evaporation. The experimentshowed the need for a least an effective amount of water to be presentto facilitate the formation of the silane hydrolyzate.

EXAMPLE 2

A total of 1.35 g (0.01 mole) trichlorosilane was added to a rapidlystirred reaction mixture of 1.18 g (0.15 mole) CuO (stoichiometricamount) in 25 mL ethyl acetate containing an effective amount of waterto initiate the reaction. No exotherm was observed to take place.However, the black copper (II) oxide was observed to slowly turngreen-brown in color indicating the formation of copper (II) chloride.The solution then was filtered and washed several times with distilledwater. The solvent was subsequently evaporated to yield 0.14 g (26percent yield) of an insoluble resin. This resin was shown by infraredspectroscopy to be a form of insoluble hydrogen silsesquioxane thatcontains some silanol functionality.

The effect of slowly adding the trichlorosilane to the reaction mediumand a different stoichiometry was also investigated. A total of 20.2 g(0.15 mole) trichlorosilane in 100 mL of ethyl acetate was added over a5.0 hour period to a rapidly stirred reaction mixture of 12.0 g (0.15moles) CuO in 380 mL ethyl acetate. The clear solution was then decantedaway from the brown copper (II) chloride and washed several times withdistilled water. A total of 400 mL of the solution was stored for futurecoating investigations. The remaining 80 mL was placed into evaporationdish. A total of 0.57 g (43 percent yield) of an insoluble resin wascollected after solvent evaporation. The resin was characterized byinfrared spectroscopy to be a form of insoluble hydrogen silsesquioxanethat contains some silanol functionality.

EXAMPLE 3

A total of 1.35 g (0.01 mole) of trichlorosilane was added to a rapidlystirred mixture of 1.21 g (0.015 mole) zinc oxide (stoichiometricamount) in 25 mL ethyl acetate containing an effective amount of waterresulting in an immediate exotherm. The initially cloudy solution wasobserved to become clear upon reaction followed by the precipitation ofZnCl₂. If the solutions were allowed to stand for any length of timegelation was observed to occur. If gelation had not yet occured, thesolution was filtered. An insoluble resin was then collected aftersolvent evaporation. The insoluble materials obtained either aftersolvent evaporation or from solution gelation were characterized byinfrared spectroscopy as forms of insoluble hydrogen silsesquioxane thatcontains some silanol functionality.

The above reaction was repeated using 1.82, 0.61 and 0.24 gms of ZnO, aswell as stoichiometric amounts of calcium oxide (0.83 g), copper (I)oxide (2.13 g) or magnesium oxide (0.60 g) in place of the zinc oxide.The insoluble resins which resulted were collected and characterized byinfrared spectroscopy as forms of insoluble hydrogen silsesquioxane thatcontains some silanol functionality. The results of the tests arereported in Table I below.

                                      TABLE I                                     __________________________________________________________________________    Metal                                                                             Metal Oxide                                                                           HSiCl3                                                                              Weight Ratio                                                                          Results                                             Oxide                                                                             Weight (g)                                                                            Weight (g)                                                                          MO:HSiCl3                                                                             (2% solutions)                                      __________________________________________________________________________    ZnO 1.82    1.35  2.23:1.sup.                                                                           immediate gelation                                  ZnO 1.21    1.35  1.49:1(s)                                                                             gelation after 30 min.                              ZnO 0.61    1.35  0.75:1.sup.                                                                           gelation after 24 hrs.                              ZnO 0.24    1.35  0.29:1.sup.                                                                           gelation after 24 hrs.                              CaO 0.83    1.35  1.48:1(s)                                                                             gelation after 5 min.                               Cu.sub.2 O                                                                        2.13    1.35  1.49:1(s)                                                                             gelation after 24 hrs.                              CuO 1.18    1.35  1.49:1(s)                                                                             clear solution-stable                                                         for greater than 6                                                            months                                              __________________________________________________________________________     (s) equals stoichiometric ratio                                          

EXAMPLE 4

The analytical data obtained for the insoluble hydrogen silsesquioxaneresins isolated from the reactions involving trichlorosilane and copper(II) oxide in the above Examples are summarized in Table II below.

                  TABLE II                                                        ______________________________________                                        Carbon content        1.00    percent                                         Hydrogen content      3.77    percent                                         TGA-weight loss in air                                                                              1.76    percent                                         TGA-weight loss in helium                                                                           3.77    percent                                         GPC-number avg. mol. weight (a)                                                                     848     amu                                             GPC-weight avg. mol. weight (a)                                                                     13,140  amu                                             Proton NMR            4.90    ppm (s, br)                                     Chlorine content (washed H2O)                                                                       175     ppm                                             Chlorine content (no wash)                                                                          7400    ppm                                             ______________________________________                                         (s, br) -- broad singlet;                                                     (a) Gel Permeation Chromatography data was obtained by leaching a soluble     fraction of the resin with a chlorinated solvent.                        

The small weight loss of 3.8% observed in the thermogravimetric analysisin the absence of air is indicative of that obtained for a highmolecular weight hydrogen silsesquioxane resin. The gel permeationchromatography (GPC) data was obtained on a soluble fraction leachedfrom the dried resin by a chlorinated solvent. Although most of thehydrogen silsesquioxane resin cannot be redissolved in a solvent, theGPC data indicate that a small quantity of low molecular weightextractable species was still present in the resin.

The presence of silanol moieties in the isolated hydrogen silsesquioxaneresins was observed by infrared spectroscopy. Attempts to furtherquantitate the hydroxyl content of these resins included evaluationbefore and after solvent removal. Prior to solvent removal, thehydrolyzate was found to contain approximately 4-8% by weight silanolmoieties. The silanol content in the insoluble films obtained aftersolvent evaporation was determined by an infrared spectroscopictechnique to be in the range of 2000-9000 parts per million (0.2 to0.9%). This silanol level is much higher than the 140-330 parts permillion level previously observed for the nearly fully condensed,soluble hydrogen silsesquioxane resin formed by the method of Collinsand Frye, U.S. Pat. No. 3,615,272.

All infrared data were obtained using either a Perkin-Elmer infraredspectrometer, model 783, or a Nicolet FTIR spectrometer, model 5SXB. Thechlorine analyses were obtained by neutron activation analysis performedat Dow Chemical Company. All GPC data were obtained using aHewlett-Packard gas chromatograph, model 5840A, equipped with acapillary inlet system, model 18835B, and a 30 meter DB-17phenylmethylsilicone fused quartz capillary column (0.32 diameter).

EXAMPLE 5

Hydrocarbon solvents were used to demonstrate their effect on thereaction of trichlorosilane and the subsequent gelation of the silanehydrolyzate when exposed to such hydrocarbon solvents. A total of 5.37 gtrichlorosilane was added to a rapidly stirred mixture of 4.74 g CuO in50 mL ethyl acetate containing an effective amount of water. After theclear solution was decanted away from the metal oxide, it was washedwith distilled water. A total of 50 mL of toluene was then added to theclear solution. Immediate clouding of the solution was observed tooccur. The solution was again washed with distilled water, filtered andplaced into an evaporation dish. A total of 0.11 g (6 percent yield) ofinsoluble hydrogen silsesquioxane was obtained after solventevaporation.

In another reaction, a total of 2.70 g trichlorosilane was added to arapidly stirred reaction medium consisting of 2.36 g CuO in a mixture of2 mL ethyl acetate and 25 mL toluene containing an effective amount ofwater. Hydrogen chloride fumes were observed during the water washprocedure prior to gelation of the solution. It is suspected thatminimal reaction took place prior to the wash procedure. Similar resultswere obtained using cyclohexane in place of the toluene and in a zincoxide/toluene/ethyl acetate reaction medium.

Finally, a total of 1.35 g trichlorosilane was added to a rapidlystirred mixture of 1.21 g zinc oxide in 25 mL ethyl acetate containingan effective amount of water. After the clear solution was decanted awayfrom the metal chloride, a total of 100 mL of toluene was added.Attempts to remove the ethyl acetate under vacuum resulted in gelationof the solution. Similar results were obtained using xylene in place ofthe toluene.

EXAMPLE 6

The reaction was attempted using a methyl iso-butyl ketone (MIBK)solvent. A total of 2.70 g trichlorosilane was added to a rapidlystirred mixture of 2.36 g CuO in 30 mL of MIBK containing an effectiveamount of water. The solution was observed to turn orange-brown and agreen precipitate formed within several minutes. A mild exotherm wasalso encountered. The solution was filtered and the filtrate washed 5times with 100 mL distilled water. The solution became clear in color bythe final water wash. A total of 9.5 mL of the clear solution was placedinto an evaporation dish. After the solvent had evaporated 0.29 g (86percent yield) of insoluble hydrogen silsesquioxane was collected. Therest of the clear solution was stored for investigation of stability.The solution was observed to gel within a 24 hour period. The experimentshows the suitability of MIBK as a solvent for the process of thepresent invention.

EXAMPLE 7

The reaction was attempted using a diethyl ether solvent. A total of2.70 g trichlorosilane was added to a rapidly stirred mixture of 2.36 gCuO in 30 mL diethyl ether containing an effective amount of water. Nocolor change was noticeable. The clear solution was washed four timeswith 50 mL distilled mater. During the wash procedure the solutionturned from clear to yellow, then to white and finally back to clear. Atotal of 25 mL of the clear solution was placed into an evaporationdish. After the solvent had evaporated a total of 0.27 g (30 percentyield) insoluble hydrogen silsesquioxane was collected.

EXAMPLE 8

A total of 2.55 g methyltrichlorosilane was added to a rapidly stirredmixture of 2.03 g CuO in 30 mL MIBK containing an effective amount ofwater. The reaction solution mixture was observed to change color fromblack to green over a 30 minute period. The mixture was filtered and thefiltrate was washed three times with 100 mL distilled water. The clearsolution was then placed into an evaporation dish. A total of 0.47 g (52percent yield) insoluble methyl silsesquioxane resin was collected aftersolvent evaporation.

EXAMPLE 9

A total of 1.35 g trichlorosilane and 1.28 g methyltrichlorosilane wereadded to a rapidly stirred mixture of 2.20 g CuO in 30 mL MIBKcontaining an effective amount of water. After the resulting solutionwas filtered, the clear filtrate was washed three times with 50 mLdistilled water. Then the clear solution was placed into an evaporationdish. After the solvent had evaporated, a total of 0.39 g (40 percentyield) of an insoluble copolymer of HSiO_(3/2) --(H₃ C)SiO_(3/2) with amethyl-Si:H--Si ratio of 1:1 was collected demonstrating that thereaction proceeds to form a copolymer.

EXAMPLE 10

Solutions containing a total of 5 weight percent (H₃ C) and H--Sihydrolyzates in various ratios were prepared by the addition oftrichlorosilane and methyltrichlorosilane mixtures (see Table III) to arapidly stirred solutions of MIBK (25 mL) containing an effective amountof water. The clear solutions were filtered and then washed three timeswith 30 mL distilled water. Finally, the clear solutions were stored andperiodically checked for stability.

                  TABLE III                                                       ______________________________________                                        H.sub.3 CSiCl.sub.3                                                           (mL)    HSiCl.sub.3 (mL)                                                                         H.sub.3 CSi:HSi                                                                         Reaction Results                                 ______________________________________                                        1.84    0.00       1:0       Solution stable (several                                                      months)                                          1.38    0.40       3:1       Solution stable (several                                                      months)                                          0.93    1.01       1:1       Gelation after 3 days                            0.37    1.50       1:3       Gelation after 2 days                            0.00    2.00       0:1       Gelation after 1 day                             ______________________________________                                    

EXAMPLE 11

Potassium bromide discs were coated with several of the hydrolyzatesolutions prepared in the above examples. Both methyl and hydrogensilane hydrolyzates in ethyl acetate were used. Additionally, to some ofthe hydrolyzate solutions, 50 parts per million of tin 2-ethylhexanoate, nickel iodide, or platinum acetylacetonate catalysts wereadded. Other samples included no catalysts.

The coated discs were then oxidized in air at 150° C. for one hour. Thepresence of silanol (Si--OH) moieties could not be determined byinfrared spectroscopy in any of the heated samples after one hour. Athermal H--Si redistribution reaction was observed by infraredspectroscopy for both the catalyzed and uncatalyzed reactions. The testswere repeated for other coated discs at 300° C. for one hour. However,the thermal H--Si redistribution reaction could not be observed forsamples containing the platinum, nickel, or tin catalysts. Oxidation ofthe Si-H moieties was observed by infrared spectroscopy to occur withinthe 150°-300° C. temperature range.

EXAMPLE 12

Several unprotected silicon CMOS devices (Motorola 4011 devices packagedat Norsk Industries) were coated with samples of the hydrogen, methyl,and copolymer silane hydrolyzates prepared in the above examples.

The samples were coated onto the devices using a spin coating procedureat 3000 rpm for a period of 10 seconds. The coated devices were thenoxidized in an air atmosphere at 400° C. for one hour.

An 80x magnification of each coated surface showed the coatings to be inexcellent condition. These coated devices, along with several uncoatedcontrol devices were then exposed to salt spray conditions in accordancewith method 1009.4 MIL-STD 883C. The salt spray system used was anAssociated Environmental Systems, Model MX-9204.

The coated devices were removed from the salt spray chamber after 10minutes and then rinsed with purified water. The devices were thenheated to 100° C. for 15 minutes to evaporate any remaining water. Thedevices were then tested on a Teradyne Analytical Circuit TestInstrument, Model J133C. The devices which passed the test were againsubjected to the salt spray. This sequence was repeated every two hoursuntil all of the devices failed.

The results, which are reported in Table IV below, show that thehydrolyzates of the present invention provided better protection to thedevices than did commercially available spin-on glasses. Also, thehydrolyzates of the present invention performed similarly to fullycondensed hydrogen silsesquioxane resin (100-150 ppm platinum catalyst)prepared by the method of Collins and Frye, U.S. Pat. No. 3,615,272.

                  TABLE IV                                                        ______________________________________                                        Sample                      Time to Failure                                   Number    Material (e)      (hr.) (2 devices)                                 ______________________________________                                        7770-50-7 H--Si hydrolyzate  7.5 and 11.5                                     7770-62-1 H--Si hydrolyzate 3.0 and 3.5                                       7770-56-6 methyl-Si hydrolyzate                                                                           5.0 and 7.5                                       7770-58-1 methyl-Si (2.5 wt. percent)                                                                     1.0 and 3.5                                                 and H--Si (2.5 wt. percent)                                                   hydrolyzates                                                        --        Hydrogen silsesquioxane                                                                         8.5 (a)                                                     (condensed)                                                         --        Controls (no coatings)                                                                          0.2 and 0.2                                       ______________________________________                                        Spin-On Glasses                                                               ______________________________________                                        Accuglas 305                                                                            methylsiloxane SOG                                                                              2.0 (b, c)                                        Accuglas P-172                                                                          phosphosilicate SOG                                                                             2.0 (b, c)                                        Glassclad TF                                                                            polyethoxyacetoxy silane                                                                        2.0 (b, d)                                        (PS235)                                                                       Glassclad SO                                                                            silane ester      2.0 (b, d)                                        (PS222)                                                                       ______________________________________                                         (a) equals average of 12 devices, range equals 4.5-16.0 hours                 (b) equals testing of 5 devices                                               (c) commercially available from Allied Chemical                               (d) commercially available from Petrarch Systems, Inc.                        (e) The hydrogen silsesquioxane (condensed) sample is the only material       that contained a platinum oxidation catalyst (100-150 ppm).              

While certain representative embodiments and details have been shown forpurposes of illustrating the invention, it will be apparent to thoseskilled in the art that various changes in the methods and apparatusdisclosed herein may be made without departing from the scope of theinvention, which is defined in the appended claims.

What is claimed is:
 1. A method for the formation of a protectivecoating of a silsesquioxane resin on a substrate comprising the stepsof:a) coating said substrate with a solution comprising a non-sulfurcontaining polar organic solvent containing therein a composition of theformula (RSi(OH)_(x) O_(3-x/2))_(n) where R is a hydrogen or a methylgroup, provided R is at least 50% hydrogen, n is an integer greater thanabout 8, and x is a number between 0 and 2, and where the silanolcontent in said composition is from about 1-10% by weight, and b)evaporating said solvent and thereby deposit an insoluble silsesquioxanecoating on said substrate.
 2. A method for the formation of a ceramic orceramic-like coating on a substrate comprising the steps of:a) coatingsaid substrate with a solution comprising a non-sulfur containing polarorganic solvent containing therein a composition of the formula(RSi(OH)_(x) O_(3-x/2))_(n) where R is a hydrogen or a methyl group,provided R is at least 50% hydrogen, n is an integer greater than about8, and x is a number between 0 and 2, and where the silanol content insaid composition is from about 1-10% by weight, b) evaporating saidsolvent and thereby deposit an insoluble silsesquioxane coating on saidsubstrate, and c) converting said silsesquioxane coating to a silicondioxide-containing ceramic by subjecting said coating to an oxidizingatmosphere at a temperature of between about 100° to about 1000° C. 3.The method of claim 2 in which said solution containing said compositionis coated onto said substrate by spray coating, dip coating, flowcoating, or spin coating.
 4. The method of claim 2 in which saidsubstrate is an electronic device.